An isolated perfused cat lung will be used to: 1) define the pulmonary hemodynamic effects of prostaglandin infusion in terms of vascular resistance, sites of action, and distribution of arterial, capillary and venous blood volume. Ether and dye transit-time methods will be used for determining arterial and total vascular volumes, respectively. Capillary volume will be determined from the carbon monoxide diffusing capacity at two PAO2 levels. 2) identify those mechanisms within the whole lung which are responsible for inactivation of prostaglandins. This will be accomplished by determining the transit-time across the lung for a radioactive label contained in prostaglandins which are rapidly injected into the pulmonary artery. The time-concentration-curves for the appearance of the label in prostaglandins and their metabolites in the venous effluent will be analyzed in terms of the degree of inactivation and conversion to metabolites, and in terms of transport mechanisms within the lung. Using these methods we will also determine how prostaglandin metabolism and release of metabolites are affected by various experimental conditions and models of lung disease.